Quarter Wave Research Articles

Rapid Separation of Enantiomeric Impurities in Chiral Molecules by a Self-Referential Weak Measurement System.

We propose a self-referential fast detection scheme for a frequency domain weak measurement system for the detection of enantiomeric impurities in chiral molecules. In a transmissive weak measurement system, the optical rotation (OR) is used to modify the pre-selected polarization state and the post-selection polarization state. We obtained the sum and difference of the optical rotations produced by the sample and the standard by rotating the quarter wave plate in the system. Then, we estimate the ratio of chiral molecules to enantiomeric impurities using the ratio of the central wavelength shifts caused by the addition and subtraction states described above. In this paper, our system has an optical resolution of 1.88 × 10−5°. At the same time, we completed the detection of the ratio of the two substances in the mixture of L-proline and D-proline in different proportions, which proved that our system can quickly detect the content of enantiomeric impurities in chiral molecules.

High-speed polarization imaging of dynamic collagen fiber realignment in tendon-to-bone insertion region.

A high-speed polarization imaging instrument is demonstrated to be capable of measuring the collagen fiber alignment orientation and alignment strength during high-displacement rate dynamic loading at acquisition rates up to 10kHz. The implementation of a high-speed rotating quarter wave plate and high-speed camera in the imaging system allows a minimum measurement acquisition time of 6ms. Sliced tendon-to-bone insertion samples are loaded using a modified drop tower with an average maximum displacement rate of 1.25 m / s, and imaged using a high-speed polarization imaging instrument. The generated collagen fiber alignment angle and strength maps indicate the localized deformation and fiber realignment in tendon-to-bone samples during dynamic loading. The results demonstrate a viable experimental method to monitor collagen fiber realignment in biological tissue under high-displacement rate dynamic loading.

Polarization calibration of wide-field-of-view interference polarization imaging spectrometer

A wide-field-of-view interference polarization imaging spectrometer (WFVIPIS) is described conceptually. As a novel means of remotely detecting the polarization information of the object, the polarization calibration for the WFVIPIS is a basis and prerequisite of information quantification. In order to improve the accuracy of the polarization information acquisition of the object, an experimental scheme of the polarization calibration for the WFVIPIS is first proposed based on the laser, polarizer, analyzer and quarter wave plate, and its feasibility is demonstrated. The detailed and accurate calibration experiment is performed in Xi'an Jiaotong University, and the polarized calibration equations on various Stokes vectors parameters of the monochromatic linear polarization light, monochromatic circularly polarization light and complex linear polarization light are obtained by the data processing. This work establishes the quantitative relation between the output signal from the WFVIPIS and the Stokes parameters of the incident light, which lays the foundation for the quantitative applications of the polarization remote sensing information.

Fast phase-shifting technique for 3-D surface micro-topography measurement

This paper presents a two-step phase-shifting interferometry technique for fast inspection of uniformity of optoelectronic samples. The in-line configuration was applied to make full use of the space-bandwidth product (SBP) of the camera and hence can resolve finer spatial details of the sample. Two-step phase-shifting (TSPS) algorithm was used to reconstruct the object with only two in-line interferograms generated when a quarter wave plate (QWP) is placed in the light path of one arm of the Mach-Zehnder interferometer. Experimental results show that the extracted phases calculated by the TSPS technique match with the phases extracted by the three-step phase-shifting (THSPS) technique.

Compact, high gain, linearly polarized diversity antenna for KU band applications

AbstractThree elements multiple input multiple output (MIMO) antenna operating in Ku band is proposed in this article. Antenna elements are fed by simple line feeding technique. Matching between feeding line and radiator is maintained by adding quarter wave transformer between them. To reduce overall size of the MIMO system, three similar antenna elements are allocated on single radiator on the top face of single substrate. Wide bandwidth is achieved by etching square slot in the elliptical shape radiator. High isolation between two antenna elements is attained by placing antenna elements λ/8 distance apart. Simulated and measured results (S11 < −10 dB, S12/S13 < −18 dB) demonstrate proposed antenna is appropriate for Ku band applications. The diversity characteristics and diversity gain are also studied by calculating envelope correlation coefficient. High gain of MIMO antenna is achieved by increasing number of elliptical radiators. Linear polarization is due to parallel orientation of all radiating antenna elements. The proposed antenna is suitable for satellite applications.

Comparison between Trigonometric, and traditional DDS, in 90 nm technology

The Direct Digital frequency Synthesizer (DDS) is an architecture largely used for the generation of numeric sine and/or cosine waveforms in different applications. In this work, authors compare two different DDS architectures: the traditional architecture, based on the exploitation of quarter wave symmetry, and the Symon’s DDS (trigonometric DDS) presented in 2002. The two layout configurations have been implemented in 90 nm technology and compared in terms of area, speed and power consumption. Comparisons have been performed in terms of circuital complexity on architectures having the same Spurious Free Dynamic Range (SFDR) and phase resolution. Experiments show that the trigonometric architecture is very efficient in terms of area.

Laser Induced Damage Threshold of Ta2O5 and Ta2O5/SiO2 Films at 532 and 1064 nm

Laser induced damage threshold (LIDT) of conventional electron beam deposited Ta2O5 and SiO2 thin films on BK-7 substrate are studied to see the effect of multilayer boundary and related effect for their combination as high and low index material films when number of layers increases as well as improvement on upper two non-quarter wave thickness layers. Reflection spectra of these samples show a relatively small decrease in reflection in non-quarter wave layer design and Grazing Incidence X-ray Diffraction (GIXRD) patterns show that deposited films are amorphous, having high (4.2 eV) band gap, sufficient high refractive index and very low extinction coefficient or low absorption which are factors favourable for high laser induced damage threshold. LIDT measured for single layer at 1064 nm is higher than that of multilayers and vice-versa at 532 nm wavelength. However, improvement of LIDT with non- quarter wave outer layers is more at 532 nm than 1064 nm.

Vacuum ultraviolet quarter wave plates based on SnTe/Al bilayer: Design, fabrication, optical and ellipsometric characterization

Vacuum ultraviolet and extreme ultraviolet polarized light plays a significant role in many applications from materials science and solar physics investigations to optical components development. In this paper, we study the optical performances and the quarter wave retarder properties of aluminum coating capped with SnTe/Al thin film. The measurements have been performed by using a reflectometer properly improved for ellipsometric characterizations. The specimen has been fully characterized at hydrogen Lyman–alpha line (121.6 nm) by deriving the reflectance and the ellipsometric parameters, i.e. the ratio r and the phase difference δ. We found that the SnTe/Al bilayer behaves as phase retarder, although the performances differ from the ideal case. In fact, the polarimetric analysis combined with the optical test at different wavelengths allowed to identify carbon contamination on the top layer and a mild oxidation of the aluminum coating that affect the optical throughput.

Reflection of Blue Light Using Bi-Layer Al2O3–TiO2 E-Beam Coating Films

E-beam deposition was used to deposit Al2O3 and TiO2 single-layer films onto glass substrates at 300 °C, with 6 sccm O2 being introduced during the deposition process. Optical characterization of the films was conducted to evaluate whether the thickness was suitable for the formation of multipair reflective coatings. The refractive indices of the films measured at an optical wavelength of 450 nm were 1.742 (Al2O3) and 2.206 (TiO2). E-beam deposition was then used to deposit Al2O3–TiO2 bilayer films in one, two, four, and six periods on glass substrates to fabricate multilayer films as broadband Bragg-reflecting coatings for blue light. The thicknesses of the Al2O3 and TiO2 films for the quarter wave condition were 51 and 64 nm, respectively. When one period of Al2O3–TiO2 bilayer film was deposited on the glass substrate, the film had high transparency, and no reflective effect was observed. As two, four, and six periods were deposited on the glass substrates, the Bragg reflection effect became apparent. T...

Simultaneous measurement of retardance and fast axis azimuth based on liquid crystal wave plate group

The simultaneous measurement of retardance and fast axis azimuth based on liquid crystal wave plate group (LCWPG) is presented. The laser beam propagates through an aperture and then splits into two beams by a non-polarizing beam splitter (NPBS). The intensity of the reflected beam is detected by a photomultiplier tube (PMT) as the reference light intensity. The transmitted beam, which passes through a polarizer, a quarter-wave plate, a retarder sample to be measured and the LCWPG successively, is finally detected by another PMT. The LCWPG is composed of four liquid crystal wave plates (LCWPs). In addition, the LCWPG works in six different polarized modulation modes dependent on the voltages applied on each LCWP. The six corresponding sets of light intensity are then measured by the two PMTs. By calculating and deriving from the six sets of light intensity, the retardance and fast axis azimuth of the measured sample can be obtained, respectively. In the experiment, the retardance of a quarter wave plate as the sample is measured when its fast axis is at different angles. The standard deviations of the retardance and the fast axis azimuth of the measured sample are 0.67˚ and 0.85˚, respectively. The effectiveness of the proposed method is verified.

Review on Resonator and Muffler Configuration Acoustics

Nowadays, resonators are widely used in automobile, industrial applications, aerospace engineering, and some other fields. One of the unique characteristics of resonators which made them highly convenient is their acoustic capability to attenuate noise without having to use any acoustic absorptive material. The device acts by manipulating the sound waves to create mismatch impedance. Recent studies also suggest that the typical bulk size resonator with narrow frequency bandwidth is not the only option anymore, since there are newly designed resonators that are capable of having wide attenuation bandwidth and are smaller in size. Numerical and experimental measures were executed accordingly with the same purpose to obtain efficient noise attenuation results from varying resonators’ and mufflers’ configuration in terms of quantity, types, and geometry. The aim of this review is to summarize recent developments on resonator study and to try highlighting some noteworthy issues that need to be unraveled by future research. Helmholtz resonator, Quarter wave tube, Herschel-Quincke tube and helicoidal resonator are part of the numerous resonator studies that will be covered in this paper.

A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D.

A Faraday-effect-based radial-interferometer-polarimeter diagnostic has been developed to explore fast magnetic dynamics in high-performance DIII-D plasmas. The instrument measures radial magnetic field perturbations using three chords positioned near the magnetic axis. Newly developed solid-state sources operating at 650 GHz provide phase noise down to 0.01°/ and tunable bandwidth up to 10 MHz. Various systematic errors which can contaminate the polarimetric measurement have been investigated in detail. Distortion of circular polarization due to non-ideal optical components is calibrated using a rotating quarter wave plate technique. The impact of perpendicular magnetic field, i.e., the Cotton-Mouton effect, is evaluated. The error due to non-collinearity of probe beams is minimized to less than 0.5° for electron density up to 7 × 1019 m-3 by alignment optimization. Optical feedback, due to multiple reflections induced by the double-pass configuration, is identified and reduced. Coherent and broadband high-frequency magnetic fluctuations for DIII-D H-mode plasmas are observed.

Full linearly stokes interference imaging spectropolarimeter based on channeled polarimetric technique with high optical throughput

A static full linearly Stokes interference imaging spectrpolarimeter (FLCIISP) over 400–800 nm spectral range is presented. The FLCIISP system includes an achromatic quarter wave plate, a high order retarder and a Savart interferometer. The instrument employs tempo-spatially mixed modulated mode without internal moving parts, offers a robust system and a high optical throughput to resist the instrument noise. The feasibility of the system was verified by simulation and laboratory experiments. Compare with the conventional channeled interference imaging spectropolarimeter, the resolution of the reconstructed spectrum is remarkably improved and the errors in reconstructed spectral Stokes parameters caused by aliasing are suppressed effectively.

16‐4: Study of Anti‐reflection Thin Polarizer for pOLED Display

We studied anti‐reflection conditions in plastic Organic Light Emitting Diodes (pOLED) display to obtain a uniform neutral black in all of viewing angles. Well‐known anti‐reflection design is consist of retardation (Rin) and wavelength dispersion of a quarter wave plate. However, we realized that a viewing angle anti‐reflection condition is determined by a total out plane retardation (Rth) of a polarizer. We defined Rin & Rth behaviors related with reflectance of pOLED display. These researches can be achieved better products appearance by obtaining the best anti‐reflection conditions.

P‐73: Broadband Quarter Wave Plate by Coating Technique

Broadband quarter wave plates are widely used in optical system, especially in display system. Above all, a broadband quarter wave plate can be treated as an isolator in display to provide “perfect” dark state so as to improve the contrast ratio. A kind of broadband quarter wave plate combined by two waveplates with angle deviated is proposed and manufactured in this paper using coating technique. Two methods of combination of the two waveplate are proposed and tried. The reflection spectrum shows that this kind of structure can provide good dark state in display system.

22.1: Fabrication of Broadband Quarter Wave Plate by Combination of Two Retardation Films Using Coating Technique

22.1: Fabrication of Broadband Quarter Wave Plate by Combination of Two Retardation Films Using Coating Technique

Full linearly Stokes channeled polarimetric technique with low reconstruction errors

A novel full linearly Stokes channeled polarimetric technique is presented. The system includes an achromatic quarter wave plate, a high order retarder and interference imaging spectrometer. The principle of the system is verified by simulation. Compare with the conventional channeled polarimetric technique, the resolution of the reconstructed spectrum is remarkably improved and the errors in reconstructed spectral Stokes parameters caused by crosstalk are suppressed effectively. A compensation procedure is proposed to account for the alignment errors. An analytical treatment is given, followed by a numerical example to demonstrate the effectiveness of the compensation method.

Terahertz polarization converter based on all-dielectric high birefringence metamaterial with elliptical air holes

Metamaterials have been widely applied in the polarization conversion of terahertz (THz) waves. However, common plasmonic metamaterials usually work as reflective devices and have low transmissions. All-dielectric metamaterials can overcome these shortcomings. An all-dielectric metamaterial based on silicon with elliptical air holes is reported to achieve high artificial birefringence at THz frequencies. Simulations show that with appropriate structural parameters the birefringence of the dielectric metamaterial can remain flat and is above 0.7 within a broad band. Moreover, the metamaterial can be designed as a broadband quarter wave plate. A sample metamaterial was fabricated and tested to prove the validity of the simulations, and the sample could work as a quarter wave plate at 1.76 THz. The all-dielectric metamaterial that we proposed is of great significance for high performance THz polarization converters.

Invited Article: An active terahertz polarization converter employing vanadium dioxide and a metal wire grating in total internal reflection geometry

Active broadband terahertz (THz) polarization manipulation devices are challenging to realize, but also of great demand in broadband terahertz systems. Vanadium dioxide (VO2) shows a promising phase transition for active control of THz waves and provides broadband polarization characteristics when integrated within grating-type structures. We creatively combine a VO2-based grating structure with a total internal reflection (TIR) geometry providing a novel interaction mechanism between the electromagnetic waves and the device, to realize a powerful active broadband THz polarization-controlling device. The device is based on a Si-substrate coated with a VO2 layer and a metal grating structure on top, attached to a prism for generating the TIR condition on the Si-VO2-grating interface. The grating is connected to electrodes for electrically switching the VO2 between its insulating and conducting phases. By properly selecting the incident angle of the THz waves, the grating direction, and the incident polarization state, we first achieved a broadband intensity modulator under a fused silica prism with an average modulation depth of 99.75% in the 0.2-1.1 THz region. Additionally, we realized an active ultra-broadband quarter-wave converter under a Si prism that can be switched between a 45° linear rotator and a quarter wave converter in the 0.8-1.5 THz region. This is the first demonstration of an active quarter-wave converter with ultra-broad bandwidth performance. Our work shows a highly flexible and multifunctional polarization-controlling device for broadband THz applications.

Vectorial diffraction properties of THz vortex Bessel beams.

A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.